Process and apparatus for the thermal treatment of minerals in powdery form

Abstract

A process and apparatus to treat powdered minerals placed in gaseous suspension by thermal exchange. The process includes the steps of preheating the minerals to be treated by the exhaust gas from a furnace. The minerals are then treated in the furnace. The minerals are then cooled with a stream of air prior to introducing the stream of air into the furnace. The furnace exhaust gases are filtered before being released into the atmosphere. A majority of the filtrate is mixed with the minerals leaving the furnace. The remainder of the filtrate is placed in suspension in a current of air diverted from the current of warm air which cools the minerals leaving the furnace. The remainder of the filtrate is separated from the air. The remainder of the filtrate is then mixed with the treated minerals and at least partially cooled. The diverted air is mixed with the furnace exhaust gases.

What is claimed is: 
     
       1. A process for treating powdered minerals suspended in a gas by heat exchange, comprising the steps of: preheating the minerals to be treated by the exhaust gas from a furnace;   treating the minerals in the furnace;   cooling the minerals with a stream of air prior to introducing the stream of air into the furnace;   filtering the furnace exhaust gases before releasing the exhaust gases into the atmosphere;   mixing a majority of the filtrate with the minerals leaving the furnace;   placing the remainder of the filtrate in suspension in a current of air diverted from the current of warm air which cooled the minerals leaving the furnace;   separating the remainder of the filtrate from the diverted air;   mixing the remainder of the filtrate with the treated minerals at least partially cooled; and   mixing the diverted air with the furnace exhaust gases.   
     
     
       2. The process according to claim 1, additional comprising the step of a fuel into the diverted air.   
     
     
       3. An apparatus with an outlet for treating powdered minerals suspended in a gas, comprising: a furnace with an intake and an exhaust;   two sets of cyclones having inlets and outlets, including a first set of cyclones located upstream of the furnace and a second set of cyclones located downstream of the furnace;   a plurality of pipes serially connecting said furnace exhaust to said first set of cyclones and serially connecting said second set of cyclones to said furnace intake;   a filter for removing dust from said exhaust;   an auxiliary exchanger including an auxiliary cyclone with an intake and gas and dust outlets and a auxiliary pipe which connects the intake of said auxiliary cyclone to one of said outlets of one of said cyclones of said second set, said gas outlet of said auxiliary cyclone being connected to one of said plurality of pipes connected to one of said outlets of on of said cyclones of said first set; and   means to feed said auxiliary exchanger with a portion of the filtered dust and said auxiliary cyclone having a diameter smaller than that of the cyclones of said two sets of cyclones and having a greater efficiency than the cyclones of said two sets of cyclones.   
     
     
       4. The apparatus as claimed in claim 3, wherein said auxiliary exchanger includes a burner.   
     
     
       5. The apparatus as claimed in claim 3, wherein said dust outlet of said auxiliary cyclone is connected to the outlet of the apparatus.   
     
     
       6. The apparatus a claimed in claim 3, additionally including a supplementary cooler having an input connected to said second set of cyclones and a output connected to the outlet of the apparatus, said dust outlet of said auxiliary cyclone being connected to said input of said supplementary cooler positioned between said second set of cyclones and the outlet of the apparatus.